A processing system consumes power as it operates. For example, a processing system associated with a mobile computer might consume power from a battery. As the performance of a processing system is improved (e.g., by increasing the speed of the processor, allowing wireless communication, providing a larger display, and/or executing more complex applications), the amount of power consumed by the processing system may increase. As a result, a battery may need to be re-charged more frequently, which might be annoying for a user. Note that increasing the size of the battery might be impractical (e.g., because it would make a mobile computer too large).
To conserve power, a processing system and/or a subsystem within the processing system may have a number of different power states. For example, the processing system or subsystem might operate in a higher-power state when it is actively being used and in a lower-power state during periods of relative inactivity (e.g., a hard disk drive might be transitioned to a lower-power state when it has not been accessed for five minutes). In some cases, however, a processing system or subsystem may not be transitioned to a lower-power state. For example, a subsystem might not be placed in a placed in a lower-power state even when a user is not executing any applications that require that subsystem.